There are several devices which will fit on to a standard ball hitch, but these are not suitable for simple launching trolleys. I use a portable electric winch (https://www.superwinch.com/products/winch-in-a-bag-2000-1120149 ) and a 12 volt power-pack for pulling my rib up the beach.
I use a "Shoprider" electric scooter (made for the disabled) I fitted a tow hitch to the back of it. I use a 12ft ali dinghy and fitted wheels to the transom on ali brackets facing upwards. So dinghy is towed upside down. I fitted a spigot at the bow to drop into the hole in the hitch. I tow it about 400 metres from home down a steep hill then back up again after sailing.
it does not however go well in soft sand and gets bogged easily. (differential rear axle like a car. so in effect one wheel drive) It suits me fine now for 2 seasons. A new set of batteries cost around 175 squid the old gopher itself a similar price second hand and battered. I occasionally use it to go to the club in lieu of walking. I feel a bit of an OAP but it goes well. I charge mine from solar panels on the roof. Might not suit everyone but at least I am all set up for being aged.
olewill
I know this is an old thread but I've jsut come across it. I use an electric mobility scooter to move my partly built ISO based trimaran around: https://www.youtube.com/watch?v=IvAEP-EzUnA